Messages in this thread Patch in this message |  | | Date | Mon, 28 Jan 2013 19:30:33 -0600 | From | Kim Phillips <> | Subject | [RFC] arm: use built-in byte swap function |
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Enable the compiler intrinsic for byte swapping on arch ARM. This allows the compiler to detect and be able to optimize out byte swappings, e.g. in big endian to big endian moves.
AFAICT, arm gcc got __builtin_bswap{32,64} support in 4.6, and for the 16-bit version in 4.8.
Signed-off-by: Kim Phillips <kim.phillips@freescale.com> --- akin to: http://comments.gmane.org/gmane.linux.kernel.cross-arch/16016
based on linux-next. Depends on commit "compiler-gcc{3,4}.h: Use GCC_VERSION macro" by Daniel Santos <daniel.santos@pobox.com>, currently in the akpm branch.
RFC because of unfamiliarity with arch ARM, and that at91sam9rl, at91rm9200, and lpd270 (so far, at least) builds fail with:
include/uapi/linux/swab.h:60: undefined reference to `__bswapsi2'
I'm using eldk-5.2.1/armv7a's arm-linux-gnueabi-gcc (GCC) 4.6.4 20120303 (prerelease)
arch/arm/Kconfig | 1 + include/linux/compiler-gcc4.h | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index eda8711..437d11a 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -3,6 +3,7 @@ config ARM default y select ARCH_BINFMT_ELF_RANDOMIZE_PIE select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE + select ARCH_USE_BUILTIN_BSWAP select ARCH_HAVE_CUSTOM_GPIO_H select ARCH_WANT_IPC_PARSE_VERSION select BUILDTIME_EXTABLE_SORT if MMU diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h index 68b162d..da5f728 100644 --- a/include/linux/compiler-gcc4.h +++ b/include/linux/compiler-gcc4.h @@ -67,7 +67,8 @@ #ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP -#if GCC_VERSION >= 40400 +#if (!defined(__arm__) && GCC_VERSION >= 40400) || \ + (defined(__arm__) && GCC_VERSION >= 40600) #define __HAVE_BUILTIN_BSWAP32__ #define __HAVE_BUILTIN_BSWAP64__ #endif -- 1.7.9.7
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